Because men are paid more, on average, women in Merseyside will effectively be "working for free" until the end of the year.

According to the Fawcett Society , a charity which campaigns for women’s equality and rights, the current gender pay gap means that women in full time work effectively stopped earning relative to men just over a week into November.

This day - which fell on November 9 this year - is referred to as Equal Pay Day. Each year it varies according to the pay gap as it stands at the time. This year November 9 reflects the estimated 14.2% difference in earnings between men and women.

But why does it happen?.

Suffragettes campaigning during the Reading By-Election in 1913

Isn't it illegal to pay women less than men?

It is, but it is also difficult to prove. The Equal Pay Act 1970 was intended to stop women being paid less favourably than their male colleagues, and equalise pay and conditions. According to campaigners the pay gap has been closing but progress is slowing and it will take over 50 years to close the gap for full time workers.

Is everyone affected?

For younger women the gap is less, estimated by the Fawcett Society to be lowest for women in their twenties, around 2.6%.

However, for older women, those in the fifties this gap rises massively to 20.5%.

But it is also dependent on what kind of work you do - for example it is over 20% in the skilled trades and 19.8% for managers, directors and senior officials, while it's less than 5.1% for those working in sales and customer service.

Why does this happen?

According to researchers a major part of the problem is that some relatively low paid jobs, such as those in the care and leisure industries, are carried out by disproportionately high numbers of women compared men. Women make up 60% of those earning below the Living Wage.

Also, men continue to dominate in apprenticeships and industries with the best earnings potential - in 2013 nearly 13,000 men started engineering apprenticeships while only 400 women did.

How did it get so bad?

Caring for children and poorly relatives is still a role which falls predominantly to women, often leading to them being more likely to work part-time - 42.3% compared to 15.7% in jobs which are also typically lower paid.

Fawcett research with low paid women (earning less than £7.44 per hour) also found 10% of their sample who had recently returned from maternity leave were given a more junior role.

Prime Minister David Cameron

What is being done about it?

Earlier this year Prime Minister David Cameron announced plans to force firms to reveal data on the pay gap between men and women.

This was welcomed but the Fawcett Society is also calling for the Government to create targets for apprenticeships and aim for 50:50 recruitment, make it easier for fathers to take parental leave, and build on the extension of free childcare for three and four year olds.

So what should I do if I'm being paid less than a male colleague?

If you are being paid less than another (male) worker doing the same job you can try to work it out with your employer informally.

Failing that contact your union if you are a member and they will be able to advise and may even be able to negotiate fairer pay. For example Unison, one of the largest trade unions, has an advice page here .

And if that doesn't work you could take legal advice and even take your employer to an Employment Tribunal.